This work consists of an effort to understand the philosophical notion of personal identity over time. The means to reach this understanding is to analyse and to discuss the most important solutions found in the literature that were proposed to the problem of personal identity. This problem is described as the difficulty of grounding and explaining our belief that a person in a given moment of her life and herself in another moment are one and the same person, despite all the great biopsychosocial changes which she undergoes. The first proposed solution to this problem makes substantial criteria, whether physical or metaphysical, central to personal identity. The second solution appeals to the notion of continuity, whether physical or psychological, to explain how people remain the same over time. A third solution suggests that the problem can be solved through linguistic-conceptual analysis; here, we discuss such ideas as the sceptical conception of personal identity, selfreference, self-consciousness and the first-person perspective. And, finally, with the help of the notions of self-organization and emergence, we discuss possible contributions of systemic theory to solving the problem.